ADC crit of 1000 will give 20 more damage with 3 points in havoc.
AP heavy burst of 500 will give 10 more damage with 3 points in havoc.
Damage early game ~ 80 will grants 1,6 bonus damage with 3 points in havoc

Butcher gives you 4 bonus damage to minions when having 2 points put in to it.
Brute force gives you 3 bonus AD when putting 2 points in this mastery.
Mental force gives you 6 more AP which equals with 0,7 AP ratio 4,2 bonus damage when 3 points in this mastery.

Havoc has a clear power boost when dealing high amounts of damage.
However, if you do not, it is obviously less than the other damaging masteries presented above :D